Yesterday my e30 started generating a persistant CEL (Check Engine Light) error 1221 which indicates the o2 sensor has failed or is sensing values so far out of spec it can’t be interpretted. I suspect that driving around with a nagging misfire for almost a month fouled the sensor. The sensor is only a couple months old, which is a shame. Thankfully I kept my old sensor which I’ll use until it fails or I finally swap in a s52 engine.

February 12, 2013 mechanical, repairs

My little blue buzz bomb has been driving like it’s up to it’s bumper in peanut butter. This has been going on for 2 or 3 weeks, but generally driveability has been declining for the last 2 months. Initially I thought it was a fuel problem which wasn’t totally out there but my mechanic drove it and was 90% sure of an ignition problem on the primary side.



  • initially idles rough, runs strong once the temp. gauge starts to move (“normal” for this car)
  • runs great for 5, 10 minutes
  • at some point driving or idling CEL (1221 o2 sensor) comes on
  • at the same time sounds and acts like a cylinder is dropping
  • loss of power especially at low RPM, poor fuel economy
  • let it sit for 20-30 minutes
  • it will initially start up like the cylinder is missing with CEL still lit
  • after 20 seconds the CEL clears and it drives fine for another 5, 10 minutes
  • non-conductive spark tester thing seems to indicate it’s cylinder 5 that is misfiring

The happy ending to this is that it’s finally fixed! But I’m going to relate the story in 3 sections: what I’ve learned, what fixed the problem, and then I’ll talk about everything else I tried to fix the problem.

4 Easy Lessons

  1. Start At The Ends: To experienced trouble shooters this is probably so obvious that it’s stupid. But the “ends” of a system – where stuff is input and where stuff is output – are the best places to look for solutions. If you turn on your tap and no water comes out you wiggle the faucet, check for hot and cold and then you check to see if the rest of the house has water, right? The problem is likely at one of those two places. More complicated systems tend to be the same: check the ends, then work your way backwards from the output end.
  2. Start With The Easy Fixes:┬áIf something just needs to be cleaned, adjusted or can be eliminated with a visual or low-tech inspection then start there. Because isn’t it awesome when something is an easy fix?
  3. Diagnostics Over Parts: It’s better to run tests than throw parts at a problem. It’s cheaper and doesn’t introduce new variables. You’ll always have people telling you to replace this or that part but that’s wasteful. Save you money and energy for the really hard problems.
  4. Cleaning Is Maintenance: Cleaning your car is a chance to inspect stuff. Typically I stay out of my car’s underside because I don’t get it onto jack stands very often but I will do better in that area now.

Problem Solved: Clean the Crank Position Sensor (CPS)


Above: CPS location and closeup.

So I’ve heard of the CPS before. Heard people talk about:

  • the wires being frayed
  • adjusting it (early model e30s only, so I’ve learned)
  • it can test o.k. and still not work
  • if you have spark and fuel it must be working (confused yet?)

Generally I was confused and unsure of what to do with it, though I knew it was in scope for the problem I was having. Here’s the layman’s explanation of what the CPS does (source):

Any one of the things I’ve replaced could cause the symptoms I’ve noted, but replacing parts did nothing because the parts weren’t actually failing or bad. Other things that were blamed by people I asked:

  • CPS
  • DME (it’s a computer, almost untestable without the right equipment)
  • oxygen sensor
  • cap and rotor (even though I just replaced it)
  • HT wires

Most people want to throw parts at this kind of problem, so I’m glad it didn’t come to that for me. That’s the end of the story, so here’s some photos taken during the various fixes:

  1. Replaced the plugs because I was checking them anyways. This was #6 which looks bad but would still work in that condition.
  2. Checked the plug wire set and found that the #5 wire had a cut in it.
  3. Off to the Pick n Pull to find another wire set. This one was not perfect but it was a match and the only one available. e30s are not appearing at the dismantlers very often, right now.
  4. Dirty but nothing I can’t clean up. Discovered that some of the wires were not in good condition but had what I needed. The entire harness was only $10.
  5. Quick solution to see if the new wire makes a difference. It did not.
  6. New cap & rotor and cleaned up that harness. The wire cover is now black!
  7. Tested the coil. Seems out of spec.
  8. Borrowed a coil from a friend. Of course it made no difference.

Image Gallery

February 8, 2013 mechanical, repairs

If you own an e30 with an old fuel pump then I recommend replacing it even if it isn’t yet making death-rattle noises: the difference will be so obvious you’ll swear your e30 has more horsepower. This is a 20 minute job.

I got my pump and sender from the Pick n’ Pull for $70. Normally I would not have installed used parts in this application but I found a remarkable specimen and scooped it. If you have the means I suggest buying new for reliability and because there are so many after-market pumps available that are excellent and cheap especially if you have an engine with a higher than average LPH (litres per hour) requirement.


In my photo above you can see the new pump and sender have nice white plastic bits while my old parts are all brown. This isn’t aging it indicates a material update seen in newer fuel pumps. Expect to spend $250-280 for a new pump and sender, less if you retrofit a non-OEM pump.


The before (top) and after (bottom).

This job is dead simple and well documented. This thread on r3vlimited has some insights into noises and rusty fuel tanks. I won’t duplicate the step by step but I will share my notes on the procedure:

  • was happy to find foam seal still in place, though incorrectly installed
  • was not happy to find 1/8″ of dust covering everything
  • one of the nuts that hold the sender to the pump was missing: someone was in here before me apparently
  • cleaned up the dust as best i could, next time i’ll bring a brush and vacuum
  • stuffed paper towels all around the hoses
  • disconnected plugs and fuel hose (came off easily, no need to mangle the hose)
  • tried to block the hose with a sharpie but it was too big – a bic pen would work better
  • removed sender and put it in a bucket
  • could have used a hammer and screwdriver but just used muscle to spin & remove pump
  • pump locks onto the gas tank simular to the child-proof cap on medicine bottle
  • discovered the filter sock had fallen off and was in the tank
  • car has probably been guzzling all manner of dirt and gunk for years
  • based on that suspect fuel filter (1 year old) is gunked up and will need to be replaced next
  • went to home depot and bought a little claw to get the filter sock out of the tank
  • proceeded with new (to me) parts, clean up, etc.
  • car ran super rough initially probably due to air in the fuel line
  • eventually cleared up: car feels stronger, smoother acceleration
  • fuel guage still reading incorrect, may need to replace 2nd fuel level sender
  • filled up tank to try to dislodge sender float, will see how guage changes as i drive it
  • whole car reeks of gas, as do i.

Update (Monday 2012-01-28):

My e30 is messed up, stuttering and lacking power. Though it ran strong for an afternoon my “exceptional specimen” didn’t have much life left. Here’s how I’ve determined that the pump fuel supply is the problem: When the car stutters during acceleration, check the tachometer and fuel economy guages. If the RPMs drop that usually indicates a lack of spark. If the fuel economy drops that indicates the engine is starving for fuel.


My car is doing the latter, puttering at between 5 and 0 MPG in every gear and whenever the throttle is open. Tomorrow I’ll get up early and try hopefully swap in my old pump.

Update (Tuesday 2012-01-29):

The old pump improved drivability but I can tell it’s a short term fix because my old pump is making noise sometimes and the MPG frequently and nearly bottoms out just driving normally. This could be a combination of factors (fuel pump, fuel pressure regulator, injectors) but I suspect the pump.

This time it only took me 15 minutes to swap pumps but I’ll be doing it again soon so maybe I can do it even faster next time. There are several aftermarket pumps available but I decided on an OEM pump from TurnerMotorsport (they have the best price).

The bodger retrofit is to buy a pump and kit and rig it into the pump armature. The most common pump for that applicaiton is the Walbro 255 GSS-340 (DIY Retrofit Instructions). Cars with higher displacement engines or turbos sometimes put in a pump with greater LPH (litres per hour) such as the  Deatschwerks 300 LPH but that’s not necessary for a stock engine, even an s52 let alone an m20.

I’m a sucker for OEM.

Update (Sunday 2012-02-03):

I’m still convinced I have a fuel issue but my mechanic drove the car and says it has the tell-tale signs of a spark issue. I replaced the plugs in the 4 troublesome cylinders (which were actually o.k), replaced a cracked HT wire and swapped in the new distributor cap and rotor from my trunk kit for good measure: problem persists. If my mechanic is correct then the next item to inspect is the ignition coil.

Update (Tueday 2012-02-05):

My new OEM fuel pump arrived last night and I installed it in the dark. Works great and I can definitely feel that the car has new energy. Afterwards I drove it around the block with the pump exposed and the seat cushion off and it was crazy how loud the pump is. However my surging and powerloss issues prevail and I am going to replace the ignition coil to try to remedy that. As I’ve read, the coil can fail completely but it can also fail slowly causing exactly the symptoms I’m experiencing.

One last thing, It’s worth noting that every time I’ve done this there has been very little fuel in the hose coming off the pump, but this time there was much, much more fuel. It’s a good idea to remove the fuel sender before disconnecting the hose so you have somewhere to drain all that fuel.

How to:

Fuel Pump Replacement 

Part Numbers:

Suction Device with Pre-Supply Pump (255 LPH) 16141179415
O-Ring 16111744369
Sending Unit Assembly 16141152266 

Service Diagram (via RealOEM)

BMW e30: Fuel Pump Replacement

January 26, 2013 mechanical, repairs

I didn’t do any of the work but I learned a lesson: when part of a pressurized system fails and is replaced the next weakest weakest part is likely to fail as well. This is why when a coolant hose is replaced the shop will usually replace all the hoses.


The story:

  • before Cars & Coffee last saturday morning the clutch pedal got stuck on the floor
  • picked it up off the floor, was able to drive the car but clutch felt soft
  • did some reasearch, sounds like the clutch master or slave cylinder
  • cheap part, messy job that requires a lift and bleeding the brake fluid system
  • on monday drove the car to Bavarian Motorsport, my independant shop of choice
  • they isolated it to the clutch slave cylinder which was leaking
  • they replaced it and i drove it to work
  • when i went to leave at 11PM the clutch pedal got stuck on the floor
  • i could pressurize the system by pumping the pedal but the clutch would slowly re-engage
  • sounds exactly like clutch master cylinder failure
  • master cylinder can have a leaking inner seal but not lose fluid because it’s a closed loop and fluid will be recycled
  • next morning call AAA (more on them later) and had the car towed back
  • everything seems fine, but it might be that the clutch master cylinder is failing
  • decide to have them replace it

Got the car back today and it’s working fine. Would have loved to do the work myself but I don’t have the facilities nad it’s probably for the better as it’s a messy job. The following diagram isn’t of an e30 but it does explain how the master cylinder and slave cylinder are connected:

  1. brake fluid reservior supplies the hyrdaulic fluid for the system
  2. the clutch master cylinder creates creates pressure when the clutch pedal is depressed
  3. ….
  4. ….
  5. The clutch slave cylinder is actuated by the pressure from the clutch master cylinder and physically engages the clutch


Here are the parts from the BMW service diagrams:


Oh yeah almost forgot about AAA. So they towed my car to the shop but because the e30’s oil pan is right over the front axles their truck scraped up my pristine oil pan. Kinda cheesed about it, but I guess it’s not that big a deal.


January 24, 2013 mechanical

Car has been acting poorly for the last two weeks. Usually it stalls dead once on cold start. Then sometimes it hunts until it warms up, rarely it surges to 2.5K then settles at 1K and stays there but mostly it just bogs around 500 RPM until warm. If I leave the car off for 20-30 minutes it does bog but recovers faster. Considering the state of my spark plugs I suspect clogged injectors but I’d like to rule out a new vacuum leak first since this is classic vacuum leak behavior.

Recorded today after it stalled once on cold start, then did this:

BMW e30 Idle Hunting from Gary Gehiere on Vimeo.

November 12, 2012 mechanical, video

Sandblasted the 3 good spark plugs that I replaced the other week. These will go in the trunk bin as emergency spares since it’s obvious I’ll be needing them.


Photos: After and Before

November 12, 2012 mechanical

The e30 developed a misfire on the final leg of our Sunday tour. It’s fixed now.


  • left the car parked
  • researched the issue on the e30 forums, came up with a million different ideas (see below)
  • for good measure sent an email to my mechanic


  • got up early planning to check the spark plugs
  • didn’t have the right socket, went to Pepboy’s and bought a 21mm spark plug socket
  • my mechanic emailed me to confirm that I should start with the plugs
  • blew out each port with compressed air and removed plug #1
  • looked dirty, though later my mentor and mechanic told me that it didn’t look that bad
  • left the job as it was, Trina went and picked up “Bosch Super Plus WR8LC+” spark plugs for me


  • got up early
  • methodically loosened each plug with the breaker bar
  • removed each plug with socket driver
  • labelled each plug
  • plug #4 was pretty black, #5 was totally clogged, #6 was blistered
  • plugs were pre-gapped but checked anyways, all were .30mm
  • applied anti-seize compound to the threads on each plug and re-threaded by hand
  • tightened to finger tightness with extension and socket
  • tightened to 22 ft. lbs. with torque wrench
  • discovered tips on plugs are larger than the plugs on HT wires
  • removed plugs again and removed tip with vise grips
  • re-installed plugs
  • after stalling 2-3 times managed to keep it alive long enough for a drive around the block
  • still mis-firing, stomp code 1222 (“Lamda Control 1”, umbrella code for too much o2)
  • checked HT wires, #1 seemed just ever so slightly mis-seated at the distributor cap
  • car ran just fine after that


Wrap Up

My mechanic says based on the buildup that the problem was plug #5 and the miniscule amount that the #1 HT wire was out by would have no effect. I’m not 100% sure with that diagnosis but the car is running and I’m happy. I will sand blast my old plugs and save them for spares as I will need to replace #5 in 3,000 miles. Or less.

His sound advice is not to put any more money into this m20 engine, which could run for a long time in it’s current state. And save for an engine swap, specifically a 3.2L e36 M3 motor a.k.a S52. If I get lucky I may get the engine for $2K, but install will be a whole other matter. If I do an engine swap then I may paint the engine bay at the same time.


Photos of the worst two plugs, #5 (gap filled with buildup) and #6 (blistered):

Technicals Spec List

e30 M20 Spark Plugs: NGK ZGR5A or Bosch Super Plus WR8LC+
Spark Plug Socket Size: 21mm
Spark Plug Torque: 15 – 22 ft. lbs. 

Misfire Information

For reference, diagnosing a misfire includes (but is not limited to) the following systems / parts:

  • spark plugs
  • spark plug wire set
  • distributor cap & rotor
  • ingition coil
  • fuel pressure / fuel pump
  • fuel injectors
  • AFM (air flow meter) & related hoses 
  • vacuum leaks
  • timing belt
  • coolant temperature sensor
  • o2 sensor

October 31, 2012 mechanical, repairs

Picked up and installed some used sidemarker sockets and new bulbs (part number 63217160797). All but one of the car’s sidemarkers has been disconnected and burned out since I got the car. Some day I’d like to put clear lenses (read: make) in my markers and front turn signals but that will have to wait.

On that note, here’s a few of my non-mechanics rules to buying a used e30:

  • if someone can’t be bothered to replace a burned out bulb they probably couldn’t be bothered to do the required maintenance either. burned out bulbs are a sign of neglect.
  • avoid custom painted cars: replacement body parts cost extra because they will always need to be painted and fasteners and clips may be painted over or missing entirely.
  • almost any car looks good wet. be suspicious if someone hoses down their car before you look at it.

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October 7, 2012 mechanical, repairs

I booked the vehicle bay at Tech Shop so that I could learn to jack up my car. I’ve jacked up other cars just to change a flat but never put a car up on stands. It was a good learning experience and a chance to take a look at the under carriage. Tech Shop had 2 floor jacks but only one was short enough to fit under the front support. Here’s the diagram I used to determine where to put the floor jack and stands:


Didn’t want to but no choice but to put the floor jack under the rear differential because my muffler was blocking the optimal spot on the subframe support. While I was under there I had intended on installing the heat shield I pulled 2 weeks ago but I couldn’t figure out how to get the muffler out of the way and ran out of time (the previous guy who booked the vehicle bay held me up for almost an hour which is a big faux pas at the Tech Shop). I may try again later.

I did paint my fog light deletes and install them while at Tech Shop this morning. Observations about painting:

  • get more paint than you need. you’ll need it. i only had 2 oz and needed at least 10 oz.
  • get a gravity fed paint gun, it works better with small amounts of paint
  • bring your own acetone, don’t count on the Tech Shop having some
  • bring your own teflon tape for air hose couplings


September 30, 2012 mechanical, photos

Either my alignment wasn’t out much or there really isn’t much they can do about it. Tires shouldn’t wear unevenly now, at least.


September 16, 2012 mechanical

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